The art of printing with micro-fluid technology is relatively well known. A permanent or semi-permanent ejection head has access to a local or remote supply of fluid (e.g., ink). The fluid ejects from an ejection zone to a print media in a pattern of pixels corresponding to images being printed. Over time, the heads and fluid drops have decreased in size. Multiple ejection chips joined together are known to make large arrays, such as page-wide printheads.
In any configuration, imaging devices notoriously waste ink during maintenance operations. The larger the printhead, the more the imaging device wastes it. A page-wide head supporting 100,000 nozzles or more consumes as much as twenty times the volume of fluid of a scanning head supporting around 5,000 nozzles operated under comparable situations. The consumption wastes a quarter to a half or more of a page-wide imaging device's fluid supply on maintenance alone.
The amount of fluid actually consumed during these maintenance cycles varies greatly in page-wide devices according to usage. The heavier the usage, the fewer maintenance routines the imaging device requires to keep fresh its fluid in nozzles for printing, and vice versa. Heavy users who print frequently or who print large, multi-page imaging jobs may see only 15% or so of its fluid spent on jetting maintenance, while lighter users who print infrequently or who print smaller-sized imaging jobs may see 80% or more of its ink wasted on maintenance. There are needs in the art to overcome this problem. Any devised solutions must also appreciate that these maintenance routines prematurely shorten the life of printheads. To the extent usage dictates that only 80% of fluid ejections correspond to maintenance routines, such as those associated with light usage, only 20% of the printhead life is then available for actual imaging and needs addressing.
Requirements with heads also exist to continually keep fresh fluid for imaging. They relate primarily to water loss from the fluid that evaporates through jetting nozzles exposed to ambient conditions. As losses in their severest form can prevent the proper formation of ejection bubbles in firing chambers, imaging devices regularly cap dormant nozzles of printheads. During uncapped times, however, evaporation can occur so rapidly that imaging devices with scanning printheads periodically conduct maintenance jetting of unused nozzles when they pass outside the width of the print media at the end of a scan line. The frequency of jetting corresponds to the characteristics of the fluid. It relates to a fluid's “idle time.” A common idle time suggests that nozzles jet during imaging or maintenance every one to two seconds to prevent fluid from drying and clogging nozzles. Unfortunately, page-wide printheads can never scan outside the boundaries of an imaging width of a print media and cannot be jetted at ends of scan lines during times of nozzle uncapping like their scanning head counterparts. On the other hand, page-wide heads can be fired for maintenance between pages of an imaging job and/or before a first page and after a last page. Assuming a print speed in a page-wide configuration of one page per second, and using common idle times, each nozzle in a page-wide head requires a minimum of several firings between pages. This unfortunately further shortens the life of jetting actuators.
Accordingly, a need exists in imaging devices to better maintain nozzle health of printheads, especially in large micro-fluid arrays. The need extends not only to minimizing fluid waste during maintenance, but to lengthening head life by curtailing harmful jetting practices. Concomitant benefits that shorten fluid idle time are also sought when devising solutions. By loosening idle time restrictions regarding firing frequency of jetting actuators, ink formulations may be made free to evolve more naturally. Still other alternatives and benefits are sought with implementations of the invention.